The present invention relates to a method of and apparatus for automatically controlling an electronic flash lamp to illuminate the object being photographed, in which an electronic flash lamp apparatus automatically terminates the flash when agreement between the predetermined and actual amounts of light is reached, the predetermined amount of light being calculated depending on exposure information, namely, the object distance, the lens diaphragm aperture, etc.
In methods for automatically controlling an electronic flash lamp, it is known to terminate the flash when the actual amount of light reflected from the object being photographed reaches a predetermined amount. But in such a method, there will often be a failure to take a picture due to low light conditions because it is hard to know, prior to taking the picture, whether or not the object distance is in the range in which it is possible to take a flash exposure with success.
In another known method for automatically controlling an electronic flash lamp, the amount of light to be produced is predetermined prior to taking a picture depending on exposure information such as the object distance, the lens diaphragm aperture and film speed. Various types of electronic flash lamp apparatus for automatically controlling the amount of light to be produced are well known. One, for example, is provided with a plurality of capacitors whose capacitances are different from each other, in which the capacitors are selected to predetermine the amount of light to be produced depending on the object distance and so on. Another has only one capacitor with a relatively large capacitance, the terminal voltage of which is controlled to predetermine the amount of light to be produced.
Such methods for predetermining the amount of light to be produced have the advantage that the user can determine prior to the actual taking of pictures whether or not the amount of light required for proper exposures is within the capability of the electronic flash lamp apparatus to be used. On the other hand, the first method requires the provision of many capacitors; whilst in the second method it is difficult to control the terminal voltage at a high level.